feat: add Arknights: Endfield, and stop passing off requirements as summaries

Endfield was previously written off as undatable. That was wrong: a first
pass only inspected its Duration rows (all "Permanently Available") and its
year-less version grid, and missed an "Event | Schedule & Summary" table
whose cells read "Period: 08/09/26 - 08/30/26 During the event...". Two real
events, with a year.

Adds MM/DD/YY range parsing for that shape. Month-first ordering is not
assumed lightly — Endfield's own version grid reads 01/22, 04/17, 07/16 for
versions 1.0, 1.2 and 1.4, chronological only if the month comes first.

Also stops presenting unlock conditions as descriptions. Several templates
put "Reach Union Level 8" where a blurb would go; filling the summary slot
with text that never says what the event is is worse than leaving it empty.
Wuthering Waves correctly drops to zero summaries as a result.

Co-Authored-By: Claude Opus 5 (1M context) <[email protected]>

README.md

@@ -16,7 +16,7 @@ server, database and scheduler are specified but not built.
 | Piece | State |
 |---|---|
 | Event schema, date parsing, Game8 parser | Built, tested |
-| Five game sources (Genshin, Star Rail, Wuthering Waves, ZZZ, NTE) | Built, tested |
+| Six game sources | Built, tested |
 | Cross-source merge and conflict detection | Built, tested |
 | Web interface, offline support | Built |
 | Bun server, SQLite, refresh scheduler, review queue | Specified in `docs/`, not built |
@@ -82,15 +82,16 @@ date makes you miss content. Given the choice, this ships nothing rather than a
 | Wuthering Waves | Game8 | 10 |
 | Zenless Zone Zero | Game8 | 12 |
 | Neverness to Everness | Game8 | 13 |
-| Arknights: Endfield | — | No usable source, see below |
+| Arknights: Endfield | Game8 | 2 |
 
 Game8 uses a different page template for almost every game — label/value detail tables, column
 tables, rowspan Start/End pairs — and four different date formats between them. One parser handles
 all of it; each game costs a registry entry.
 
-**Endfield has no adapter on purpose.** Its Game8 page carries no usable dates: every duration reads
-"Permanently Available", and the schedule is an image grid showing `07/16` with no year and no end
-date. Supporting it would mean inventing both. It needs a different source.
+Endfield yields only two events because most of its page genuinely has no dates — every `Duration`
+row reads "Permanently Available" and its version grid shows `07/16` with no year. The two dated
+events hide in a combined cell (`Period: 08/09/26 - 08/30/26 During the event...`), which is where
+the `MM/DD/YY` parser earns its place.
 
 Arknights is defined in the schema and awaiting a source.